There are today many devices on the market which are primarily intended to discriminate between genuine coins and spurious coins or slugs. In view of the large number of coin-operated machines in use, it has become increasingly important to discriminate between genuine and non-genuine coins so as to minimize the losses which operators of coin-operated machines incur each year. These losses multiply rapidly as the ingenuity of man is devoted to defeating the machine instead of accommodating to it. Thus it has become a continuing contest between coin-machine operators and coin-machine users to arrive at a coin discriminating apparatus which keeps to a minimum the acceptance of spurious coins or slugs.
With many coin discriminators, which depend upon oscillators and a resonating circuit influenced by the metal of the coin to be accepted or rejected, there are various local factors which affect the criticality of the acceptance/rejection circuitry, i.e., humidity, local temperature, and environmental changes such as the proximity of metallic objects.